Heat-developable diazo-type light-sensitive material

ABSTRACT

A heat-developable diazotype light-sensitive material is provided which gives a high density of dye-image. This lightsensitive material may be produced by applying to a substrate a solution containing a diazonium compound and a derivative of polyhydroxybenzoic acid dissolved in an aqueous solution which contains a salt of an alkali metal (Na), an alkaline earth metal (Ca and Mg) or a weak acid having an electric dissociation exponent more than 2.0.

United States Patent lwata et al.

[4 1 Mar. 21, 1972 [54] HEAT-DEVELOPABLE DIAZO-TYPE LIGHT-SENSITIVE MATERIAL [72] Inventors: Susumu Iwata, Tokyo; Etuo Oida,

Yokohama-shi, both of Japan [73] Assignee: Kabushiki Kaisha Ricoh, Tokyo, Japan [22] Filed: Dec. 23, 1969 [21] Appl. No.: 887,758

[30] Foreign Application Priority Data Dec. 28, 1968 Japan ..44/781 [52] US. Cl ..96/75, 96/49, 96/91 [51] ..G03c 1/60,G03c 1/58 [58] Field of Search ..96/91, 49, 75

[56] References Cited UNITED STATES PATENTS 2,442,061 5/1948 Slifkin ..96/91 2,694,010 1l/l954 Botkin et a1.. ...96/9l R 3,140,180 7/1964 Fritz 96/49 X 3,207,603 9/1965 Savit ..96/75 3,298,834 l/1967 Eldred et al.. 96/49 X 3,416,924 l2/1968 Tummers ..96/49 3,529,964 9/1970 Kienast et al. ..96/49 X 1,770,352 7/ 1930 Murray ..96/75 2,653,091 9/1953 2,773,768 12/1956 Sanders et a1 ..96/91X 3,102,812 9/1963 Welch ..96/91 X 3,123,472 3/1964 Wilders et al... .....96/49 3,326,686 6/1967 Randall et a1 ..96/91 3,331,689 7/1967 Sosnovsky et al ..96/91 X 3,353,984 11/1967 Landau ....96/91 X 3,389,996 6/1968 Welch ..96/49 X FOREIGN PATENTS OR APPLICATIONS 957,836 5/1964 Great Britain ..96/49 957,837 5/1964 Great Britain .96/49 1,070,625 6/1967 Great Britain .96/91 1,481,966 4/1967 France ..96/75 1,078,912 8/1967 Great Britain ..96/91 1,095,292 12/ 1 967 Great Britain .96/49 6,803,228 9/1968 Netherlands ..96/91 Primary ExaminerCharles L. Bowers, Jr. Attorney-Burgess, Ryan and Hicks [57] ABSTRACT A heat-developable diazotype light-sensitive material is provided which gives a high density of dye-image. This light-sensitive material may be produced by applying to a substrate a solution containing a diazonium compound and a derivative of polyhydroxybenzoic acid dissolved in an aqueous solution which contains a salt of an alkali metal (Na), an alkaline earth metal (Ca and Mg) or a weak acid having an electric dissociation exponent more than 2.0.

4 Claims, No Drawings HEAT-DEVELOPABLE DIAZO-TYPE LIGHT-SENSITIVE MATERIAL BACKGROUND OF THE lNVENTION 1. Field of the Invention The present invention relates to a heat-developable diazotype light-sensitive material and a method for the preparation thereof.

2. Description of the Prior Art Derivatives of polyhydroxybenzoic acid may be utilized asa coupling component of the heat-developable diazotype lightsensitive material. However, these derivatives'are used in an alcoholic solution, since they are insoluble in water. The lightsensitive material prepared by applying said alcoholic solution to a substrate cannot give a high density of dye-image.

it is, therefore, an object of this invention to provide a heatdevelopable diazotype light-sensitive material which gives a high density of dye-image, and a method for preparing thereof.

SUMMARY OF THE INVENTION The present invention relates to a heat-developable diazotype light-sensitive material comprising adding to a substrate, a conventional light-sensitive diazonium compound, a derivative of a polyhydroxybenzoic acid and a salt of a metal selected from the group consisting of alkali metal (Na), alkaline earth metals (Ca and Mg) and a weak acid having an electric dissociation exponent (pKa) more than 2.0, said salt hereinafter being referred to as solubilizer."

The derivative of the polyhydroxybenzoic acid is represented by the following formula:

wherein R, and R are halogen such as Cl, Br or I, an aralkyl group or substituted alkyl group (e.g., substituted by SO H, CN, COOH or CONH and R is hydrogen, alkyl group, alkoxyl group (except rnethoxyl group), aryloxyl group, hydroxyalkyl group or hydroxyalkoxyl group.

In the copying art, it is well known that derivatives of polyhydroxybenzoic acid are used as a coupling component of a heat-developable light-sensitive material, said derivatives being subjected to decarboxylation by heating and coupling reaction with a diazonium compound to produce a dye-image. The derivatives of polyhydroxybenzoic acid are insoluble in water, but soluble in alcohol. Consequently, alcoholic solutions of said derivatives have been applied to a substrate together with diazonium compoundfor the purpose of using the derivatives as a coupling component.

However, alcohol permeates veryeasily the paper on account of its low surface tension. Therefore, when an alcoholic solution of the derivatives of polyhydroxybenzoic acid is applied to the paper, said derivative (i.e., coupling component) permeates the paper. A light-sensitive material prepared by applying the alcoholic solution of the coupling component and the diazonium compound cannot give a dye-image having high density and vividness. Besides, alcohol has disadvantages in that it is inflammable and expensive.

As a result of our studies for the purpose of eliminating the aforesaid disadvantages, we have found that the derivatives of polyhydroxybenzoic acid are soluble in an aqueous solution of the aforementioned solubilizer. On the other hand, we have already disclosed that halogen-introduced derivatives of 2,6- dihydroxy-4-methoxybenzoic acid are suitable as a coupling component of the heat-developable light-sensitive material. However, we have found that the derivatives of the aforementioned general formula also may be preferably used as a coupling component of the heat-developable light-sensitive material, are soluble in an aqueous solution of the aforementioned solubilizer and that a high density of dye-image may be obtained by using the aforementioned salts (solubilizer), ina. sensitive layer. The present invention is based on these discoveries.

Examples of the coupling components used in this invention are as follows:

COOH I COOH 2,6-dihydroxy-3- 2,6-dihydroxy-3- 2,6-dihydroxy-3-proplonamidd chloro-4-methyl-& chloroA-methylolfi-brornobenzoic acid broniobenzoic acid B-bromobenzoic ('30 OH COOH HO- OH HO- OH Cl- CHrCHnCN Br- CHzCHaCO OH 2,6-dihydroxy-1-carboxyfi-chlormphenyl-Zipropionitrile 2,6-dihydroxy-i-carboxy-5- bromophenyi-ii-propionlc acid As previously stated, salts used as a solubilizer in this invention are salts of alkali metals (Na), or alkaline earth metals (Ca and Mg) and a weak acid having an electric dissociation exponent (pKa) more than 2.0. The preferred examples of said weak acid include organic acids such as formic acid, acetic acid, propionic acid, stearic acid, halogenor cyano-introduced derivatives of said acids, tartaric acid, citric acid, adipic acid, fumaric acid, benzoic acid, gluconic acid and salicylic acid, and inorganic acid such as phosphoric acid.

Preferred examples of the solubilizer are as follows:

sodium salts of citric acid, acetic acid or tartaric acid;

calcium salts of acetic acid, benzoic acid, gluconic acid or salicylic acid,

and calcium hydrogen phosphate;

magnesium salts of citric acid, acetic acid, gluconic acid or stearic acid,

and magnesium hydrogen phosphate.

The advantages of this invention are as follows:

l. The coupling component remains on a surface of the substrate even when paper is used as the substrate, since the coupling component is applied to the substrate in the form of an aqueous solution. Consequently, a dye-image of high densi ty may be obtained by heat-development.

2. The density and vividness of the dye-image may be increased by controiling the amount of the solubilizer so that diazonium compounds having a low coupling activity (i.e., diazonium compounds giving a dye-image of a low density by conventional method) may be also utilized (see Example 3).

3. Since water can be used as a solvent, the process may be carried out inexpensively without danger of inflammation in comparison with a procedure using alcohol as a solvent.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is further illustrated by the following nonlimitative examples.

EXAMPLE 1 A light-sensitive solution was prepared from the following ingredients:

A heat-developable diazotype light-sensitive material of this invention was prepared by applying the light-sensitive solution to a substrate (e.g., a sheet or paper), precoated with silica, starch or polyvinyl acetate, and then drying it. The light-sensitive material thus obtained gave a clear blue dye-image by exposing to light following the conventional procedure and subjecting to the heat-development on heated rolls at a temperature of 150 C. for 5 seconds. The density of the dye-image was 1.0 when measured with a Photovolt densitometer, sold by Photovolt Co." For purpose of comparison, a comparative heat-developable diazotype light-sensitive material prepared by applying a light-sensitive solution, which was made from the above-mentioned ingredients without sodium citrate but using ethyl alcohol instead of water, to a substrate in the same procedure as that stated above, gave a lower vividness of the dye-image than that of this invention and a image density of0.5 by the same treatment as that stated above.

After subjecting the light-sensitive material of this invention to artificial aging by keeping it for 5 r 6 days at a temperature of 30 C. and relative humidity of 80 percent, a very slight reduction in the density of the dye-image could be detected and the fogging of the material could hardly be observed. The light-sensitive material of this invention possesses a high degree of stability.

EXAMPLE 2 Four kinds of solutions of coupling components containing 1.0, 1.5, 2.0 and 2.5 parts by weight of calcium gluconate were prepared from the following ingredients:

Parts by weight ('10 OH HO- OH Br Br (LCzOr Calcium gluconate l.0-2.5 Water 100. 0

Each of these solutions of coupling components was respectively applied to a substrate precoated in the same manner as that in Example 1 and then a solution of diazonium compound prepared from the following ingredients was applied to said substrate and the substrate was dried off.

Parts by weight CnH7 N- N,Cl )ZnCl; 0.7 C3H7 Benzamide 1.0 Thiourea 0.1 Citric acid 1.0 Water 100.0

Four kinds of the light-sensitive materials of this invention thus obtained were treated in the same procedure as that in Example 1 and the densities of the dye-image were compared. The results were as follows:

content of calcium density of gluconate (parts by weight) dye-image The density was measured with a Photovolt densitometer. A light-sensitive material containing no calcium gluconate gave a density of 0.5 and a very low clear dye-image.

EXAMPLE 3 A solution of a coupling component was prepared from the following ingredients:

A solution of diazonium compound was prepared from the following ingredients:

Parts by weight N@NgCl 08 Thiourea 0(2) .0

The solution of coupling component and then the solution of diazonium compound were applied to a precoated substrate, and dried off in the same manner as that in Example 1.

The light-sensitive material of this invention thus obtained gave a clear royal blue dye-image having a density of 1.0 by subjecting to heat-development at a temperature of C. for 5 seconds in the same procedure as that in Example l.

A certain diazonium compound (for example, the one having the following formula) can not be put to practical use, because it does not give a satisfactory density of the dye-image when developed on account of its low coupling activity.

A light-sensitive material was prepared in the same manner as that of this example except that this diazonium compound was employed instead of the above-mentioned diazonium compound and the amount of magnesium gluconate was increased to 5 parts by weight. This material gave a clear dyeimage having the density ofO.95.

In view of this result, according to the present invention, diazonium compounds of low coupling activity may also be utilized for the diazotype light-sensitive material.

We claim:

1. A heat-developable diazotype light-sensitive material comprising a substrate having a light-sensitive layer coating or coatings thereon, said light-sensitive layer coating or coatings consisting essentially of;

a. a light-sensitive diazonium compound,

b. a derivative of a polyhydroxybenzoic acid having the following structural formula:

ICO OH- HO- OH wherein R, and R are each a chlorine, bromine, or iodine atom, an aralkyl group or a lower alkyl group substituted further by a member selected from the group consisting of SO H, CN, COOl-l or -CONH group, wherein at least a chlorine, bromine or iodine atom is always present at either R, or the R, position; and R is a member selected from the group consisting of hydrogen, lower alkyl, lower alkoxy having at least two carbon atoms, a hydroxy substituted lower alkyl and a hydroxy substituted lower alkoxy group and c. a salt composed of an alkali metal or alkaline earth metal and an acid, said alkali metal or alkaline earth metal being a member selected from the group consisting of sodium, calcium and magnesium and said acid being a weak acid having an electric dissociation exponent (pKa) of more than 2.0. V 2. A heat-developable diazotype light-sensitive material as defined in claim 1, wherein said weak acid is,selected from the group consisting of formic acid, acetic acid, propionic acid, stearic acid, halogen or cyano derivatives of said acids, tartaric acid, citric acid, adipic acid, fumaric acid, benzoic acid, gluconic acid, salicylic acid and phosphoric acid.

3. A heat-developable diazotype light-sensitive material as defined in claim 1, wherein said salt is selected from the group consisting of sodium citrate, sodium acetate, sodium tartrate, calcium acetate, calcium benzoate, calcium gluconate, calcium salicylate, calcium hydrogen phosphate, magnesium citrate, magnesium acetate, magnesium gluconate, magnesium stearate and magnesium hydrogen phosphate.

4. A heat-developable diazotype light-sensitive material comprising a substrate having a light-sensitive layer coating or coatings thereon, said light-sensitive layer coating or coatings consisting essentially of:

a. a light-sensitive diazonium compound,

b. a derivative of a polyhydroxy benzoic acid having the following structural formula:

wherein R, and R are each a chlorine, bromine, or iodine atom, an aralkyl group or a lower alkyl group substituted further by a member selected from the group consisting of S0,,H, CN, -COOH or --CONH group, wherein at least a chlorine, bromine or iodine atom is always present at either R, or the R position; and R is a member selected from the group consisting of hydrogen, lower alkyl, lower alkoxy having at least two carbon atoms, a hydroxy substituted lower alkyl and a hydroxy substituted lower alkoxy group,

c. a salt composed of an alkali metal or alkaline earth metal and an acid, said alkali metal or alkaline earth metal being a member selected from the group consisting of sodium, calcium and magnesium and said acid being a weak acid having an electric dissociation exponent (pKa) of more than 2.0 and d. an acidic stabilizer. 

2. A heat-developable diazotype light-sensitive material as defined in claim 1, wherein said weak acid is selected from the group consisting of formic acid, acetic acid, propionic acid, stearic acid, halogen or cyano derivatives of said acids, tartaric acid, citric acid, adipic acid, fumaric acid, benzoic acid, gluconic acid, salicylic acid and phosphoric acid.
 3. A heat-developable diazotype light-sensitive material as defined in claim 1, wherein said salt is selected from the group consisting of sodium citrate, sodium acetate, sodium tartrate, calcium acetate, calcium benzoate, calcium gluconate, calcium salicylate, calcium hydrogen phosphate, magnesium citrate, magnesium acetate, magnesium gluconate, magnesium stearate and magnesium hydrogen phosphate.
 4. A heat-developable diazotype light-sensitive material comprising a substrate having a light-sensitive layer coating or coatings thereon, said light-sensitive layer coating or coatings consisting essentially of: a. a light-sensitive diazonium compound, b. a derivative of a polyhydroxy benzoic acid having the following structural formula: wherein R1 and R3 are each a chlorine, bromine, or iodine atom, an aralkyl group or a lower alkyl group substituted further by a member selected from the group consisting of -SO3H, -CN, -COOH or -CONH2 group, wherein at least a chlorine, bromine or iodine atom is always present at either R1 or the R3 position; and R2 is a member selected from the group consisting of hydrogen, lower alkyl, lower alkoxy having at least two carbon atoms, a hydroxy substituted lower alkyl and a hydroxy substituted lower alkoxy group, c. a salt composed of an alkali metal or alkaline earth metal and an acid, said alkali metal or alkaline earth metal being a member selected from the group consisting of sodium, calcium and magnesium and said acid being a weak acid having an electric dissociation exponent (pKa) of more than 2.0 and d. an acidic stabilizer. 